1. Field of the Invention
The present invention relates in general to video laser disc players for playing back a video signal recorded on a laser disc and displaying the played back video signal on a screen, and more particularly to an apparatus for processing a still picture in a video laser disc player, in which video signals recorded on laser discs of the CLV type as well as the CAL type can be displayed as the still pictures.
2. Description of the Prior Art
Conventionally, a video signal of one frame is recorded every one circumference (one track) on a laser disc of the constant angular velocity (CAL) type. The recorded video signal of one frame is played back and then displayed as a still picture on a screen. Thereafter, one track is jumped so that the just previously displayed video signal of one frame is again played back and displayed on the screen. The above operation is repeatedly performed to obtain the still picture. One example of this form of apparatus is shown in FIG. 1, herein.
Referring to FIG. 1, there is shown a block diagram of a conventional apparatus for processing a still picture in a video laser disc player, in which a video signal recorded on a laser disc of the CAL type is processed as the still picture. As shown in this drawing, the conventional still picture processing apparatus comprises a microcomputer 1 for inputting an external still picture signal STL and an external vertical synchronization signal VSYNC and outputting a one track jump signal 1TRK and a color burst phase correcting signal TOG by detecting an end point of an even field (second field) according to detection of the vertical synchronization signal VSYNC in a still picture mode, a one track jumping part 2 for jumping a video track of the laser disc of the CAL type by one track in response to the one track jump signal 1TRK from the microcomputer 1, and a color burst phase correcting part 3 for inverting a phase of a color burst of a video signal VIN in the still picture mode in response to the color burst phase correcting signal TOG from the microcomputer 1 and then outputting a video signal VOUT in which the phase of the color burst has been corrected.
The operation of the conventional still picture processing apparatus with the above-mentioned construction will hereinafter be described with reference to FIG. 2.
In FIG. 2, there is shown one example of the laser disc of the CAL type. The laser disc LD of the CAL type comprises two regions which are partitioned at a desired angle with respect to a rotation direction of the disc. One of the two regions is a video information region in which the video signal is recorded and the other is a blank region in which the vertical synchronization signal is recorded. The video signal recorded on the laser disc LD of the CAL type is played back by moving a pick-up along the video track of the disc. Upon inputting the external still picture signal STL in the middle of playing back the video signal from the laser disc LD of the CAL type, the microcomputer 1 scans the end point of the even field or the second field of the one frame by detecting the vertical synchronization signal VSYNC recorded in the blank region of the laser disc LD.
In the case where the vertical synchronization signal VSYNC is active and a field signal FIELD designates an odd filed or the first field of the one frame, the microcomputer 1 outputs the one track jump signal 1TRK to the one track jumping part 2. In response to the one track jump signal 1TRK from the microcomputer 1, the one track jumping part 2 jumps the video track of the laser disc LD by one track to the just previous track in a blank interval. As a result, the just previously played back and displayed video signal of one frame is again played back and displayed on the screen.
On the other hand, the color burst phase correcting part 3 inputs the color burst phase correcting signal TOG which is provided from the microcomputer 1 to prevent a discreteness of the phase of the color burst of the video signal. In response to the color burst phase correcting signal TOG from the microcomputer 1, the color burst phase correcting part 3 inverts the phase of the color burst of the video signal VIN every frame, thereby allowing the phase of the color burst to be successive.
Subsequently, upon inputting the still picture signal STL continuously, the microcomputer 1 outputs the one track jump signal 1TRK to the one track jumping part 2 every frame, thereby causing only the video signal VOUT of one frame stored on the same track to be successively outputted. As a result, the still picture can be displayed on the screen.
However, the conventional still picture processing apparatus of the one track jumping manner as mentioned above has a disadvantage in that it can display the video signal played back from the laser disc as the still picture only in the case of using the laser disc of the CAL type in which the blank region is set to a fixed region on the laser disc as shown in FIG. 2. Namely, the conventional still picture processing apparatus of the one track jumping manner cannot display the video signal from the laser disc as the still picture in the case of using the laser disc of the CLV type in which lengths of the video tracks are the same in any place on the laser disc and the blank region is thus present at random on the video tracks of the laser disc, differently from the CAL type.
Also in the conventional still picture processing apparatus of the one track jumping manner, the one track must stably be jumped in the blank interval of the laser disc to guarantee a quality of the still picture. This stable jumping operation imposes a heavy burden on a servo system. Further, the microcomputer 1 must continue to control the one track jumping part 2 in the process of the still picture. For this reason, the microcomputer 1 cannot perform other commands at that time, resulting in a difficulty in the operation of the circuitry.